There's absolutely nothing wrong with the concept of a consistent grading system (although it can never be completely consistent, even using AFA). If you have a figure that the market says is worth $500 in mint condition, and you pay someone $20 to verify that yes, it really is in mint condition, that figure is now worth $520. Not $700, not $800, not $1000. It's still the same mint figure (or comic) it was before it was graded - all you did is pay for some insurance for the buyer.
It's not the AFA that's the real problem - or the sellers who use AFA to insure that what you get is what they say you get. It's the buyers who pay ridiculous amounts because something is graded.